This invention relates to well testing valves. More particularly, but not by way of limitation, this invention relates to down hole well testing valves used to obtain pressure build-up test data from a reservoir.
In order to obtain optimum production from a reservoir, bottom hole pressure surveys are routinely performed in order to determine pertinent reservoir characteristics. As those of ordinary skill in the art will appreciate, pressure build-up test are performed throughout the life of the reservoir, which includes immediately after discovery, and also after the reservoir has been placed on secondary or tertiary recovery. These tests generally comprise a flow period, a shut-in period, followed by other flowing, and shut-in periods.
Important data is obtained during both the flowing and build-up periods. Various test can be designed such that the duration and number of flowing and build-up periods depend on the individual characteristics of the reservoir.
Another important consideration is the location of the pressure gauge in the work string being utilized. Generally, it is most desirable to have the bottom hole pressure and temperature gauges as close to the reservoir as possible in order to alleviate problems such as well bore storage and flow-back when changing the test mode from flowing to shut-in.
A significant number of reservoirs are thousands of feet deep. Therefore, in designing a pressure test, an important feature is the location of the pressure and temperature gauges.
Various designs have been attempted in the prior art. For instance, in U.S. Pat. No. 4,583,592 to Gazda, the application discloses a well test tool for closing a well at a down hole location below the well packer and near the formation to be tested. The apparatus is openable and closeable from the surface by tensioning and then relaxing the cable. The test tool has a lock mechanism which locks automatically upon entering the landing receptacle in the well bore.
In U.S. Pat. No. 4,842,064 to Gazda, the specification discloses an apparatus including a landing receptacle for placing in a well bore, preferably near the well packer, and a well test tool lowerable with instrumentations into the tubing on a flexible line and anchorable in the landing receptacle, the test tool then being operational between open and closed positions by tensioning and relaxing the flexible line to open and close the well at the down hole location.
Another well test tool is disclosed in U.S. Pat. No. 4,830,107 to Rumbaugh. The tool includes a valve lowerable into a well on a flexible line and locked and sealed in a down hole landing receptacle, the valve being openable and closable to permit or prevent flow therethrough, well pressures below the test tool being sensed and recorded by a recording pressure gauge both during periods of flow and during shut-in periods.
Also, attention is drawn to U.S. Pat. No. 4,669,537, wherein a test tool including a locking device installed in a landing receptacle, and a sleeve valve with a recording instrument attached thereto is claimed. Therefore, there are numerous designs which have been attempted with regard to attaching a down hole valve to a landing receptacle, and pressure testing the intersecting reservoir. However, the prior art designs suffer from the ability of being able to set the valve in the landing receptacle, flowing the well, and re-entering the well bore with a closing device while the well is flowing, and shutting-in the reservoir.
Therefore, an object of this invention is to provide a bottom hole pressure assembly to be landed in a landing receptacle of a well bore near a reservoir, and be able to obtain multiple flowing and shut-in pressure surveys.